The use of functional electronic circuits packaged in the "Credit Card" format is becoming widespread. The phrase "Credit Card" used to describe this format of packaging is derived from the fact that the packages are about the size of a credit card, except that the thickness is approximately 3.4 millimeters.
These cards find utility in numerous electronic systems. In personal computers they supplement or replace floppy disks by carrying software programs and data and are connected to the internal logic through a port on the side of the computer cabinet. Portable personal computers, notebook computers, and pocket diaries particularly find these cards convenient because they avoid the need for the expense, power requirements, bulk, and weight of a disk drive; the card needs only an electrical connector and minimal structural support.
Facsimile and copy machines use such cards to store data related to usage control. Typewriters and printers use such cards to store desired memory fonts. Word processors use such cards to store text. Hand-held terminals use card to store inventory control information. Electronic cash registers use cards to store price information. Controllable machinery can use cards to store automation control information. Programmable controllers can use cards to store process control data. Electronic game systems can use cards to store the specifics of games to be enacted on TV screens by the players.
Other areas that can benefit from the use of electronic circuit cards include bulk data acquisition such as in music and photography, where the desired song or picture is stored in memory devices of the card.
Presently available electronic circuit cards typically include one or more plastic-encapsulated or other types of integrated circuits solder attached to connection stripes or spots on a printed wire board. A connector is solder attached to metal lines which are formed on the printed wire board and extend to one edge of the board. The connector connects external power, signal, and ground lines to circuitry in the card. An external shell or encasement surrounds the printed wire board/connector assembly to physically protect and provide rigidity to the assembly, and to provide an aesthetically pleasing appearance. The encasement typically has top and bottom frames formed from molded plastic and bonded together along an outer edge to define an interior chamber in which the printed wire board is located. The top and bottom frames have ribs which contact and securely hold the printed wire board and connector in place. Top and bottom metal plates are bonded to the top and bottom frames, respectively, and cover openings in the top and bottom frames.
The use of a plastic frame adds significantly to the complexity, tooling costs, and tooling turn around time in electronic circuit card construction. This is due to the fact that the manufacture of a plastic frame requires the use of a mold. Whenever the size of the printed wire board or the number, location, or size of the semiconductor devices on the printed wire board is changed, a new plastic frame that will accommodate the changes is required. The fabrication of the mold for the new frame is extremely time consuming and expensive. As a result, the time and expense incurred in producing electronic circuit cards incorporating even minor design changes are significant.
The use of a molded plastic frame is also a major source of problems during assembly of the electronic circuit card. This results from the fact that molded plastic frames are easily bent and often have surface irregularities introduced during the molding process which prevent all card parts from fitting together properly.
Accordingly, a need exists for an electronic circuit card that can be produced quickly, is simple, inexpensive, and reliable, and overcomes the difficulties associated with molded plastic frames.